I bought this LG G4 couple of years back and I paid fully through T-Mobile. But after leaving United States and going to my home country I tried to use my local sim provider. But the phone says its Network Locked. Please help. Because I stopped using my Lg g4 long back and now trying to. Also it keeps on telling me to use device unlock app from t mobile. I tried its not working which shows I am not eligible but why.